Carbon Nanotubes: An Allotrope Worth More than Diamonds?

Recently I read a BBC article that both confused and intrigued me. The article was about a Stanford University engineering team and their creation, the “first computer built entirely with carbon nanotubes.” (Morgan, 2013) This reminded me of graphene, a singular sheet of covalently bonded carbon atoms in hexagonal rings, that had come up in class. Remember that graphite is one of the allotropes of carbon along with diamond and the C60 fullerene and that graphene is a single layer of the carbon sheets that make up graphite. (Graphene: World-leading Research and Development, 2012) Interestingly enough, India and Vhristi have both written on graphene, and nanotubes respectively, but through wider and more introductory lens; I hope to focus my research on the application of nanotubes in electronics. Thus with this foundation, I decided to investigate further the one claim the article brought up that really fascinated me, that carbon nanotubes could eventually replace silicon chips as the linchpin of modern electronics. (Hsu, 2013)

Carbon Nanotube Arrangements
Carbon Nanotube Arrangements

Single-walled carbon nanotubes are sheets of graphene rolled up into a cylinder; depending on the direction in which the sheet is rolled, the nanotube will possess different physical properties. (Nanocyl, 2009) Extreme strength, up a hundred times stronger than steel, while maintaining lightness is one of the characteristics that have made scientists so interested in carbon nanotubes. (Bonsor & Strickland, 2007) The other is the ability to act as a semiconductor, a substance with conductivity less than that of most metals but greater than that of an insulator. (Forbus) Currently, the heart of the ubiquitous tablets, computers, and smartphones is the silicon transistor, a semiconductor switch that allow for the control of electrical signals. (Brain, 2001) To keep up with society’s demand for smaller, lighter, and faster devices, engineers have had to shrink transistors. (Hsu, 2013) However as silicon transistors get smaller, with the smallest being Intel’s 22-nanometer Ivy Bridge model, more of the energy that goes in is transformed into heat and wasted. This physical limitation has prompted research into carbon nanotubes as an alternative because of their minute size and “energy-efficiency at small sizes.” (Hsu, 2013)

So, after establishing that carbon nanotubes, theoretically, could outclass the silicon chip I went back to the BBC article to ask: what does this ‘landmark computer’ really mean for the future of carbon nanotube technology? While the computer the Stanford team, led by Subhasish Mitra and H.S. Philip Wong, created is only an elementary prototype that can only count to 32, it is definitive proof a computer could be made solely from nanotubes. (Morgan, 2013) The process in which they arrived at the computer also made great strides in use of nanotubes in electronics. The team aligned the naturally misaligned nanotubes in chips with only 0.5% disparity, designed an algorithm to bypass those that were skewed, and vaporized the “metallic” nanotubes that always conducted electricity. (Shulaker, Hills, Patil, Wei, Chen & Wong, 2013) Although these improvements have streamlined the process of creating carbon nanotube based nanoelectronics the 8000-nanometer transistors are still far from being able to compete economically or technically with silicon chips. (Palmer, 2012)

Carbon Nanotube Transistor
Carbon Nanotube Transistor

Given that silicon chips will eventually reach their limits, this test has shown that carbon nanotubes are progressing as a viable replacement for the current industry standard. (Hsu, 2013) An economic implication of this development is that if the nanotubes keep making significant progress, this possibly more efficient option to the silicon chip will be met with great demand in our technology driven society from firms and governments, the former to produce the next-generation of electronics, and the latter to improve domestic technological and military infrastructure. Just like the silicon chip allowed for a surge in technological innovation, carbon nanotubes could too engender its own rush of progress. A more short-term implication of this auspicious advancement will be reenergized investment and resources dedicated to nanotube research by firms and laboratories not wanting to be beaten to the possible patent of the next half century. But for carbon nanotubes to make the transition from laboratory to factory to store shelf will be costly and time-consuming. One must consider the economic and technological quandaries that will undoubtedly arise as this technology advances, as with all innovations. How can we mass-produce carbon nanotube transistors? How do we maintain a high quality when dealing with such tiny basic components? Each is a question that must be resolved before this new technology hits the shelves.

But I have to say, after reading about the nanotube computer I felt genuinely excited. I know that many obstacles stand in the way of carbon nanotube devices, especially the development of a cost-effective means of mass-producing nanotube transistors. On the surface this seems like a classic case of a scientifically sound theory without any means of practical execution but in this case I have hope. Ever since I have remembered I’ve been waiting for that futuristic advancement that really ushers in a new technological age like home computers and mobile phones did in the 1990s. If this it, I have hope that some combination of entrepreneurship, capitalism, and scientific curiosity will see carbon nanotube technology commercially possible, if not in our smart houses, supercomputers, and flying cars.

References:

BBC. (2011, May 04). Intel unveils 22nm 3d ivy bridge processor. Retrieved from http://www.bbc.co.uk/news/technology-13283882

Brain, M. (2001, April 25). How semiconductors work. Retrieved from http://electronics.howstuffworks.com/diode1.htm

Forbus, K. D. (n.d.). http://www.qrg.northwestern.edu/projects/vss/docs/power/3-whats-a-semiconductor.html. Retrieved from http://www.qrg.northwestern.edu/projects/vss/docs/power/3-whats-a-semiconductor.html

Hsu, J. (2013, September 26). Carbon nanotube computer hints at future beyond silicon semiconductors. Scientific American, Retrieved from http://www.scientificamerican.com/article.cfm?id=carbon-nanotube-computer-hints-at-future-beyond-silicon

Morgan, J. (2013, September 25). First computer made of carbon nanotubes is unveiled. Retrieved from http://www.bbc.co.uk/news/science-environment-24232896

Nanocyl. (2009). Single-wall nanotubes (swnt). Retrieved from http://www.nanocyl.com/en/CNT-Expertise-Centre/Carbon-Nanotubes/Single-wall-Nanotubes-SWNT

Palmer, J. (2012, October 12). Carbon nanotubes fit by the thousands onto a chip. Retrieved from http://www.bbc.co.uk/news/science-environment-20086402

Shulaker, M. M., Hills, G., Patil, N., Wei, H., Chen, H. -., & Wong, H. -. P. (2013). Carbon nanotube computer. Nature, (501), 526-530. Retrieved from http://www.nature.com/nature/journal/v501/n7468/full/nature12502.html

(Graphene: World-leading Research and Development, 2012)The University of Manchester.(2012). Graphene is going to revolutionize the 21st Century. Retrieved 24 December, 2012, fromhttp://www.graphene.manchester.ac.uk.

Image Sources:

Groeben, N. V. D. (Photographer). (2013, September 25). Hand holding cnt wafer [Web Photo]. Retrieved from http://news.bbcimg.co.uk/media/images/70097000/jpg/_70097572_handholdingcntwafer.jpg

How Stuff Works. (Designer). (2007, October ). Nanotechnology [Web Photo]. Retrieved from http://static.ddmcdn.com/gif/nanotechnology-6.gif

One thought on “Carbon Nanotubes: An Allotrope Worth More than Diamonds?

  1. After three different blog posts covering the topic of graphene, it seemed to me that this relatively new compound/discovery will become the next big industry. As David said in his blog post, graphene is a single sheet of graphite. From what I have read through different blog posts and news articles, graphene is extremely light and strong (Novoselov et al., 2012). It also act as a semiconductor for the production of carbon based computing. All these properties are wonderful and sound almost impossible to achieve. How is it that a nanotube of carbon can be magnitudes thinner and lighter than any material yet posses a greater tensile strength than that of steel? I decided to focus my research on the production of graphene; how scientists and researchers make the seemingly impossible material.

    To review, graphene is an allotrope of carbon, structured as a single sheet of sp2 hybridized carbon atoms. This allows the carbon atoms to form bonds with 3 other atoms, leaving one delocalized electron in the pi orbital above and under the sheet of graphene. The delocalized electron allows for the conduction of electricity due to the delocalized electron being freely able to move about the compound (La Fuente, n.d.). What’s surprising is the fact that it is a single sheet of atoms, meaning that graphene is extremely thin. One drawback to the structure of graphene is it’s ability to fold upon itself, making it difficult to separate itself back into a single sheet. From this, I see that the challenge in producing graphene is factored by the ease of creating a single layer and preventing any creases or folds within the sheet.

    Image: First isolation of Graphene (http://www.graphene.manchester.ac.uk/images/story/diagram1.jpg)

    Before I look into more modern ways of producing the allotrope, I looked at the first production of graphene. In 2004, Researchers at The University of Manchester created the first isolated sheets of graphene by using tape and granules of graphite. Tape was miniscule pieces of graphite and slowly remove layers of graphite at a time. The process was repeated until a single layer of graphite was achieved (Graphene, n.d.). Since then, researchers across the world have developed methods on mass producing graphene more efficiently. In 2012, Case Western Reserve University and researchers in South Korea discovered a way to produce graphene as thin as 5 sheets. To begin, graphite was first chilled and broken into pieces using dry ice [CO2(s)] in a canister filled with steel balls. The graphite was extracted and treated with carboxylic acid. Treating graphite in carboxylic acid allowed the graphite to be soluble in polar solvents, such as methanol and water. However not specified, the graphite was placed into a certain solvent, allowing the graphite flakes to form into graphene sheets (Mayhood, 2012).

    The Case Western Reserve University’s method of producing graphene is cheap; but it sacrifices the quality of the graphene by only producing graphene 5 atoms thick at minimum. In December 2013, researchers in the National University of Singapore took a different approach in creating graphene. Instead of reducing graphite into thin layers, the scientists “grew” a single layer of graphite between a copper catalyst and a silicon wafer. Once the graphene sheet was produced, the copper catalyst is slowly removed, leaving the graphene attached to the silicon wafer, while allowing for easy removal. The method of growing graphene in a single layer wasn’t first performed in this study. However, this process of producing graphene prevents any folds or creases in the graphene, improving the quality of the graphene (National University of Singapore, 2013).

    It seems like researchers world wide have produced multiple ways of producing graphene. Even though the discovery of graphene was 10 years ago, this is not to say that research of producing the highest quality of graphene has been completed. A big implication of this research relates to the seemingly endless uses of graphene. From electronics, to cars and even airplanes, graphene has been very flexible in a multitude of applications. When the cheapest and most efficient way of producing graphene is discovered, the technology industry will begin to transition into carbon based machines, increasing the efficiency, reducing the weight, and improving strength in all electronics.

    References
    Graphene: World-leading Research and Development. (n.d.). Manchester Graphene (The University of Manchester). Retrieved January 9, 2014, from http://www.graphene.manchester.ac.uk/story/
    La Fuente, J. d. (n.d.). Properties Of Graphene. Graphene Properties. Retrieved January 7, 2014, from http://www.graphenea.com/pages/graphene-properties
    Mayhood, K. (2012, March 26). Simple, cheap way to mass-produce graphene nanosheets | think:blog. Simple, cheap way to mass-produce graphene nanosheets | think:blog. Retrieved January 9, 2014, from http://blog.case.edu/think/2012/03/26/simple_cheap_way_to_massproduce_graphene_nanosheets
    National University of Singapore (2013, December 12). Novel bio-inspired method to grow high-quality graphene for high-end electronic devices.
    Novoselov, K. S., Fal’ko, V. I., Colombo, L., Gellert, P. R., Schwab, M. G., & Kim, K. (2012, April 5). A Roadmap for Graphene. Nature. Retrieved January 9, 2014, from http://www.nature.com/nature/journal/v490/n7419/full/nature11458.html

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